chemistry of the atmosphere Flashcards
For how long as the proportions of gases in the atmosphere have been much the same as they are today?
- For 200 million years, the proportions of different gases in the
atmosphere have been much the same as they are today:
What percentage of our atmosphere is made up of nitrogen?
- About 4/5 (approx. 80%)
What percentage of our atmosphere is made up of oxygen?
- About 1/5 (approx. 20%)
What makes up the rest of our atmosphere?
- Small proportions of various other gases, including carbon
dioxide, water vapour and noble gases.
Why is evidence for the early atmosphere limited?
- Evidence for the early atmosphere is limited because of the time scale of 4.6 billion years.
- Theories about what was in the Earth’s early atmosphere and how
the atmosphere was formed have changed and developed over
time.
What does one theory suggest about the formation of the early atmosphere? (Phase One)
- One theory suggests that during the first billion years of the Earth’s existence there was intense volcanic activity
- This released gases that formed the early atmosphere
- Volcanoes also produced nitrogen which gradually built up in the atmosphere & there may have been small proportions of methane and ammonia
What does one theory suggest about the formation of the early atmosphere? (Phase Two)
- When water vapour in the atmosphere condensed it formed the oceans
- Lots of CO2 was removed from the early atmosphere as it dissolved in the oceans
- Later, marine animals evolved
- Green plants an algae also evolved and absorbed some of the CO2 so they could carry out photosynthesis
What does one theory suggest about the formation of the early atmosphere? (Phase Three)
- As well as absorbing CO2, green plants and algae produced oxygen by photosynthesis
- Algae evolved first
- Then over the next billion years or so, green plants also evolved
- As percentage of oxygen built up in the atmosphere over time, more complex life (animals) could evolve
- Eventually about 200 million years ago, the atmosphere reached a composition similar to how it is today
What did the shells and skeletons of marine animals contain?
- Some of the carbonates from the ocean
How are fossil fuels/ sedimentary rocks formed?
- When plants, plankton and marine animals die, they fall to the seabed and get buried by layers of sediment
- Over millions of years they become compressed and for sedimentary rocks, oil and gas - trapping the carbon within them
- These fossil fuels form reservoirs under the seabed where they get trapped in rocks
Name sedimentary rocks
- Coal
- Limestone
What is coal made from?
- Thick plant deposits
What is limestone mostly made of?
- Calcium carbonate deposits from the shells and skeletons of marine organisms
What are crude oil and natural gas formed from?
- Deposits of plankton
What may have the early atmosphere been similar to?
- At the start of this period the Earth’s atmosphere may have been like the atmospheres of Mars and
Venus today - Consisting of mainly carbon dioxide with little or no oxygen gas.
What caused oceans to form?
- The condensation of water vapour in the atmosphere
What happened when the oceans formed?
- When the oceans formed carbon dioxide dissolved in the water
- The dissolved CO2 went through a series of reactions to form carbonates precipitates
- The carbonates were precipitated producing sediments on the seabed
- This reduced the amount of carbon dioxide in the atmosphere
What first produced oxygen and when?
- Algae first produced oxygen about 2.7 billion years ago
Explain how the oxygen that is now in the atmosphere is produced
- Algae and plants produced the oxygen that is now in the atmosphere by photosynthesis
Name the word equation for photosynthesis
- carbon dioxide + water —> glucose + oxygen
Name the symbol equation for photosynthesis
- 6CO2 + 6H2O —> C6H1206 + 6O2
How is the level of oxygen in our atmosphere increased?
- Algae & plants produced the O2 - photosynthesis
- Algae first produced oxygen and soon after this oxygen appeared in the atmosphere
- Over the next billion years plants evolved, more oxygen was produced
How was carbon removed from our atmosphere?
- The shells and skeletons of marine animalscontained some of these carbonates from the ocean
- Some CO2 absorbed by green plants and algae
How was the level of carbon dioxide in our atmosphere decreased?
- Algae and plants decreased the % CO2 in the atmosphere by photosynthesis
- CO2 was also decreased by the formation of sedimentary rocks that contain carbon (e.g. limestone and coal)
- And by the production of fossil fuels from the remains of dead plants and animals when they decayed
What is the purpose of greenhouse gases?
- Maintain temperatures on earth high enough to support life
Name greenhouse gases
- Water vapour,
- CO2
* CH4
Explain the greenhouse gas effect
- Electromagnetic radiation at most wavelengths (both long and short) from the sun passes through the Earth’s atmosphere
- The Earth absorbs some radiation and thus warms up (essential for life on Earth). But some heat is radiated from the Earth as infrared radiation.
- Some of this IR radiation is absorbed by greenhouse gases in the atmosphere
- Atmosphere warms up leading to the greenhouse effect and global warming
What do human activities cause an increase in?
- Activities increase levels of CO2 & CH4
Name human activities which contribute to an increase in greenhouse gases in the atmosphere
- Burning fossil fuels
- Agriculture (raising livestock)
- Deforestation
- Creating waste / decay of organic waste in landfill sites
How can burning fossil fuels affect the amount of greenhouse gases in the atmosphere?
- Carbon that was ‘locked up’ in these fuels is released as CO2
How can deforestation affect the amount of greenhouse gases in the atmosphere?
- Fewer trees mean less CO2 is removed from the atmosphere via photosynthesis
How can agriculture affect the amount of greenhouse gases in the atmosphere?
- More farm animals produce more ethane through their digestive processes
How can creating waste affect the amount of greenhouse gases in the atmosphere?
- More landfill sites and more waste from agriculture means ore CO2 and methane released by decomposition of waste
What do many scientists believe based on peer reviewed evidence in terms of human activity and the Earth’s atmosphere?
- Based on peer-reviewed evidence, many scientists believe that human activities will cause the temperature of the Earth’s atmosphere to increase at the surface
- This will result in global climate change
Why is peer review of results and communicating results to a wide range of audiences important?
- So you know that the information is reliable
Why is it hard to fully understand the Earth’s climate?
- Because it is difficult to model such complex systems as global climate change - there are so many variable
- It is hard to make a model that isn’t oversimplified
- This leads to simplified models, speculation and opinions presented in the media that may be based on only parts of the evidence and which may be biased or only some of the information give.
What is a major cause of global climate change?
- An increase in average global temperature is a major cause of climate change
What are the potential effects of global climate change?
- Extinction of species
- Melting of polar ice caps
- Migration
- Decrease in crop yield for all major world crops
- Changes in rainfall pattern
Why might global climate change increase migration?
- People will move from areas suffering drought/flooding
What is the effect of melting polar ice caps?
- Rising sea levels
- Increased flooding in coastal areas & coastal erosion
What is the effect of changes in rainfall pattern?
- May cause some regions to get too much or too little water
- May affect the ability of certain regions to produce food
Define carbon footprint
- The total amount of CO2 and other greenhouse gases emitted
over the full life cycle of a product, service or event.
Why is it very hard to measure the total carbon footprint of something?
- There are many different factors to consider
How can we reduce our carbon footprint?
- It can be reduced by reducing emissions of carbon dioxide and methane
Give example on how we can reduce our carbon footprint
- Using less electricity so less fossil fuels are used
- Using an renewable energy sources
- Reducing the amount of travel or transportation of either goods or people)
- Planting more trees.
- Governments could create a GHG tax based on the amount of GHG someone emits
- Using more efficient processes - conserve energy & cut waste
Why is it difficult to reduce our carbon footprint?
- Action may be limited because it’s more difficult and can be more expensive
- Many renewable energy technologies are still quite expensive
- Governments are worried about making changes to reduce GHG emission - could impact economic growth
- Planting trees takes away land that could be used to grow crops.
- Hard to make international agreements to reduce emissions
- Hard to get people to make changes if they don’t want too - lack of education
What is a major source of atmospheric pollutants?
- Combustion of fuels is a major source of atmospheric pollutants
What do most fuels contain?
- Most fuels ( including coal) contain carbon and/or hydrogen and may also contain some sulfur
Name the gases that are released into the atmosphere when a fuel burns
- Carbon dioxide,
- Water (vapour)
* Carbon monoxide, - Oxides of nitrogen (which are formed at high temperatures).
- Solid particles and unburned hydrocarbons may also be released, forming particulates in the atmosphere
What happens if there is not enough oxygen during combustion?
- If there’s not enough oxygen, some of the fuel doesn’t burn – this is partial/incomplete combustion.
- Here, solid particles of soot (carbon), carbon monoxide and unburnt fuel are released.
List atmospheric pollutants
- Carbon monoxide
- Sulfur dioxide and oxides of nitrogen
- Particulates
What happens during combustion?
- During combustion, the carbon and hydrogen in the fuels are oxidised to form carbon dioxide and water
- The combustion of hydrocarbons releases energy.
What are the properties of carbon monoxide?
- It is colourless and odourless so not easy to detect
How can carbon monoxide impact us and the environment?
- Toxic gas which can stop your blood from carrying oxygen around the body - binds to haemoglobin that normally carries O2 - lack of oxygen can lead to fainting, coma, or death
How are nitrogen oxides created?
- From a reaction between the nitrogen and oxygen in the air, caused by the heat of burning
e.g. internal combustion engines of cars
How is sulfur dioxide released into the atmosphere?
- During the combustion of fossil fuels that contain sulfur impurities - the sulfur in the fuel becomes oxidised
How can sulfur dioxide and oxides of nitrogen impact us and the environment?
- When mixed with water in clouds, they form dilute sulfuric acid or dilute nitric causing acid rain - this kills plants and damages buildings and statues, also makes metal corrode
- Causes respiratory problems in humans if breathed in
How can particulates impact us and the environment?
- Bad for the environment as it reflects sunlight back into space, meaning less light reaches the Earth, causing global dimming
- If inhaled, they can get stuck in the lungs and cause damage - leading to respiratory problems & human health problems
